Oval intensifications associated with polar arcs

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Abstract
The existence of large scale auroral forms in the high latitude region poleward of the auroral oval has generated much interest in recent years because of the implications these forms have for magnetospheric topology. Often these so called polar cap arcs are observed to be connected to auroral regions which are identified with plasma sheet particle populations. These connection points are sometimes associated with intensifications in the auroral distribution. Observations with the Viking UV Imager show that these intensifications are highly dynamic on time scales of minutes, being sometimes suggestive of substorms. The polar arcs may move in response to the dynamics of the intensification or else remain spatially fixed.